Su problema se puede resolver utilizando Dynamic Pivoting. Mire esto artículo
Prueba esto
DECLARE @t TABLE(Id_Contract INT, Dt DATETIME,Amount INT)
INSERT INTO @t SELECT 1,'2012-01-01 00:00:00.000',500
INSERT INTO @t SELECT 1,'2012-03-01 00:00:00.000',450
INSERT INTO @t SELECT 2,'2012-09-01 00:00:00.000',300
INSERT INTO @t SELECT 3,'2012-08-01 00:00:00.000',750
DECLARE @cols AS VARCHAR(MAX), @query AS VARCHAR(MAX);
SELECT
Id_Contract
, LEFT(DATENAME(month,Dt),3) + ' ' + DATENAME(Year,Dt) AS Month_Year_Name
,Amount
INTO #Temp
FROM @t
WHERE Dt BETWEEN '01/01/2012' AND '03/31/2012'
SELECT @cols = STUFF(( SELECT DISTINCT
'],[' + t2.Month_Year_Name
FROM #Temp AS t2
ORDER BY '],[' + t2.Month_Year_Name
FOR XML PATH('')
), 1, 2, '') + ']'
SET @query = 'SELECT Id_Contract, ' + @cols + ' FROM
(
SELECT
Id_Contract
, Amount
, Month_Year_Name
FROM #Temp
) x
PIVOT
(
MAX(amount)
FOR Month_Year_Name in (' + @cols + ')
) p '
EXECUTE(@query)
DROP TABLE #Temp
// Resultado
Id_Contract Jan 2012 Mar 2012
1 500 450
Editar
Para sus datos de prueba,
DECLARE @t TABLE(Id_Contract INT, Dt DATETIME,Amount INT)
INSERT INTO @t SELECT 1,'2012-01-01 00:00:00.000',500
INSERT INTO @t SELECT 1,'2012-03-01 00:00:00.000',450
INSERT INTO @t SELECT 2,'2012-03-01 00:00:00.000',450
INSERT INTO @t SELECT 3,'2012-08-01 00:00:00.000',750
la salida es
Id_Contract Jan 2012 Mar 2012
1 500 450
2 NULL 450
Avísame si cumple con el requisito.
